What exactly are Meet and Greets (M&Gs) all about?  Are they held by agencies?  Do other providers show up as well?  Where are they typically held?  And don't you risk running into a friend or co-worker?  Just curious.

you can also use the search function to find threads on it.  That's probably why no one has responded so far.  However, a M&G (or mixer) is a party hosted by a well-known monger and or provider that's a gathering at which well-screened hobbyists and mingle with top local providers. Usually two dozen of each, though it varies.
The purpose is so the former can see the latter up close and personal to get a better idea what the gals look like in person and what they are like to be with.  You can also meet fellow hobbyists, who generally introduce themselves by their handle so you can recognize them if they have a board presence.  Sometimes there's light sex play at these parties, but not always.  Some which are held in strip clubs permit girls to take guys to the VIP room for sex.  At others, usually held in hotel rooms, guys will leave with providers to have a session.  You need to be known to the host/hostess to get invited and be thoroughly screened.  Some people will not attend them because the want to retain their anonymity.  I think they're a blast.  The price for mongers is usually about $100.  Ladies get in free.